Michael,
Sounds like you have got it covered. I have been tempted to take the 500E to an event instead of the Porsche just to see how it does. Judging from your experience, it sounds like with fresh fluid & my stock brakes I could get 15 min. or so per run group of good track time before I started having issues. I might give it a shot this season just for grins. I would loved to see the look on some of my Porsche buddy's faces when my big 'ol Benz smokes a few of their butts.
Jay